It is known in the field of optical communications to provide an optical transceiver module, that is, a device that can act as both a transmitter and a receiver, in the form of a rectangular circuit board, with electrical connectors at one of the ends of the circuit board and with optical components at the opposite end of the circuit board. Optical transceiver modules typically have one of a number of standard forms, examples being Small Form Factor (SFF) modules and pluggable Small Form Factor (SFP) modules. These standard forms have known dimensions.
The optical components include transmitter optical components, for example including a laser for generating an optical signal for transmission along an optical fiber. The optical components also include receiver optical components, for example including a photodetector, for converting optical signals received along the optical fiber into electronic signals.
The electrical connectors include an input connection, for receiving an input electronic signal, and an output connection, for passing an output signal to further electronic devices.
The optical transceiver module then includes an integrated circuit, which includes signal processing functionality. For example, the integrated circuit may include an amplifier, for amplifying received electronic signals from the receiver optical components, such that they are suitable for passing to the output electrical connection. The integrated circuit may further include driver circuitry, for receiving an input electronic signal from the input electrical connectors, and for converting the received signal into a form suitable for passing to the transmitter optical components.
Integrated circuits are typically provided in the form of integrated circuit packages, in which pads on the integrated circuit itself are connected by means of bond wires to package landings, and then to connectors such as pins, around the periphery of the package. It is necessary for the integrated circuit package to be able to fit into the standard dimensions of the optical transceiver modules in which it is intended to be used.
One known integrated circuit of this type is the VSC7964 circuit, available from Vitesse Semiconductor Corporation.
However, one disadvantage with the use of the known integrated circuits is that they can not conveniently be fitted into the optical transceiver modules in which they are intended to be used. Specifically, the integrated circuits are intended to operate at very high speeds, for example receiving and transmitting data at rates of 1 GBps or more. At these high data rates, it is highly desirable for the electrical signal paths on the optical transceiver modules to be as short and straight, and as well-matched in length, as possible. In the case of the known integrated circuit packages, however, their use in an optical transceiver module requires the use of signal paths which are not straight, and whose lengths differ.
Moreover, it is advantageous for the bond wires, connecting the pads on the integrated circuit itself to the package landings around the periphery of the package, to be as short, and as well-matched in length, as possible. However, this is difficult to implement in a way which allows use of the integrated circuit package in an optical transceiver module.